The present invention generally relates to the problem of the generation of a voltage which is high enough for starting a discharge lamp by means of excitation of a resonant circuit in the region of its resonant frequency. In the prior art, in this case in particular the output voltage of the resonant circuit is measured or is swept over the entire range of resonant frequencies which is possible as a result of tolerances, i.e. alternately from lower to higher frequencies and then from higher to lower frequencies etc. In the case of the first procedure, in this case the output voltage of the resonant circuit is measured, in particular using a voltage divider, in order thereby to select the suitable excitation frequency for the resonant circuit. If it is assumed that the starting voltage is in the region of several kV, the elements of the voltage divider need to be designed for this high voltage. Moreover, the measurement of the output voltage requires a considerable amount of complexity in terms of additionally required components, which is reflected in undesirably high costs. Since the voltage at the output of the resonant circuit is present as an AC voltage owing to the inverter, it is necessary to provide a filter during measurement of said voltage in order to eliminate the AC component, with this filter resulting in additional complexity in terms of components and fitting. In the second variant, i.e. in the case of sweeping, fewer components are required, but sweeping the entire range of possible resonant frequencies which are subject to tolerances results in a low mean output voltage and therefore in the starting conditions being impaired.